Carnie b



Dec. 22 1925. 1,566,819

C. E. CARTER PROCESS OF PRODUCING METHYLALS Filed July 26, 1924 Patented Dec. 22, 1925.'y

UNITED STATES 1,566,819 PATENT OFFICE.

CARNIE CARTER, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO.S. 'KARPEN & BROS., F CHICAGQ, ILLINOIS, A CORPORATION OF WEST VIRGINIA.

rnocnss or PRODUCTNG METHYLALS.

Application led July 26, 1924. Serial No. 728,461.

To aZZ whom it may concern:

Be it known'that I, CARNm B. CARTER, a citizen of the United States, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Processes of Producing Methylals, of which the following is a specification. u

The present invention ertains to a process for producing methylals in an economical manner.

The methylals are double ethers derived, ordinarily,by the condensation of formaldehyde with alcohols, Water being elimina-ted. Various methylals can be prepared in this Way by using various members of the alcohol series. f

According to the present invention, the methylals can be produced rommethylene chloride, which is a by-product obtained fromfthe chlorination of natural gas, for example. The present invention enables methylene chloride, for Which there is little or no commercial demand, to be utilized in producing methylals; and methylals may,in turn, be used in the production of various materials, such as formaldehyde and hexamethylenetetramine, Which are widely used in the arts.

Methylals are very stable substances in neutral or alkaline solutions but are very unstable in the presence of acids. In the presence of aqueous acids they hydrolyze readily to formaldehyde and the correspondv ing alcohol inaccordance with the following equation, for example: CllsOCHZOCHH-HEO :'QCH3OH-l-'CH2O- Dimethyl methylal may thus be hydrolyzed in aboutrone hour by heating with acidulated Water at a temperature of 100 C. Very pure formaldehyde may bepropared in this way, since it is possible to prepare methylals of high purity.

In accordance with the present invention, methylene chloride is caused to react with a suitable alkali metal hydroxide in alcoholic solution., Under proper conditions, this gives rise to a large yield of methylal, the kind of methylal obtained beineN dependent upon the kind of alcohol use Mas a solvent. The yields are determined in large measure by the concentration of alcohol used. Yields approximating 90% or more of the theoretical value can be obtained in (a) oH,oH+NaoH=NaocH,+H,o. (b) cnzclgarenaooru: y

eHaooHZocHa-teNaol. (C) oH2o12+2Nao I CH2O+H20+2NaCL Thus, it seems that/the alkali in solution acts both as such and as an alcoholate, only the portlon acting as an alcoholate beingof `value in the production of methylal the remainder giving rise to free formaldehyde. The free formaldehyde subsequently is acted upon by the alkali and consumed in accordance With one or both of the two reactions Which follow:

Reaction (d) results in the production of formate and methyl alcohol; Whereas reaction (e) is very complex, m parts of the formaldehyde condenslng under the influence of the alkali to form very complex sugar-like bodies and liberating Water. There are various reasons for assuming that tle equations given above anism of the action talin place when methylene chloride and alco olic solutions are caused to react upon each other.

Methylene chloride reacts With an alcoholic solution of sodium hydroxide at ordi-A nary temperatures, but the reaction is too Slow to be of practical importance. At Such temperature, the reaction is only 4% to 5% complete after 150 hours. The reaction velocity increases rapidly with rising temperature and becomes of practical importance in the neighborhood of C. to 60 C., at which temperature reaction is complete in about 75 to 100 hours. At a temperature of 100 C., reaction is complete in about 3 hours; and at 125 C., in about 40 to 50 minutes.

A temperature of 100 to 125 C. is a satisfactory working temperature for practicev of the process, the corresplonding pressure'v being in the neighbor ood of 100 pounds per squaresilich. At a lower temperature, the pressurepis lower. For exortray the mechample, at about C., the pressure does not rise much above atmospheric pressure. While Aa temperature as 10W as 60 C. may be employed, the time for completing the reaction is unduly prolonged; and it is preferred, therefore, to practice the process at a temperature materially above 60 C.

The reactions take place in solutions of high alcoholic content; they also take place yin vsolutions of lower alcoholic content, but

.process/if a large yield of methylal is to be secured. that the reaction be performed in relatively dilute alkalisolution, it' being noted that water is produced in the reactlon, as indicated in equation (a) above.v

Thus, two mols of water are produced for each mol'of methylal formed, inasmuch astwo mols of the aleoholate are required for each mol offmethyial produced.l To keep the` water content low, the reaction should takeplace ina solutiqn of high alcoholic content and low sodium hydroxide concentration. w I I While the equations given above, in v1ew of the foregoing'explanation, will suffice to indicate proportions to be used, the following may be given as an exampleof sultable proportions and a suitable mode of proceure:

Charge into an autoclave I100 gallons of salcohol; 10 gallons of methylene chloride;

and about 110 pounds of caustic, such as sodium hydroxide. Heat the autoclaveat a temperature of 100 to 125 C; for the requisite period, usually about forty minutes; and, iinally. separate the methylal by a su1table procedure, such as that hereinafter described. i From the batch given above, there should be produced about 10 to 1l gallons ofmethylal, which is a yield of about 85%.

The process may be practiced conrveniently by apparatus such as that shown dlagrammatically in the accompanying. drawing;

and the process may be described conveni- `entlywith reference to the ldraw-mg.

A represents a supply tank containing .methylene chloride; B, a supply tank con.

taining methyl alcohol; C, asupply tank containing sodium hydroxide; D, an auto clave,r which may be provided with suit, able means for heating, and which preferably also is equipped with a suitable stirring device; E, a filter, which is employed for separating the salt formed (sodium/chloride in the example given) from the filtrate; F, a storage chamber for the sodium chloride; G, a still, where the alcohol and methylal may be fractionally distilled, the alcohol passing through the line H to the storagetank B, and the methylal passing to the storage-tank I; J, an evaporator from which the`sodium hydroxide may be returned through the line K-to the storage-tank C;

L, a hydrolyzer, wherelhel'nethylal may be treated for theprodiu-'lion of formaldehyde; M, a still receiving the mixturefron'i the hydrolyzer and from which the alcohol formed may pass through the, line O to the storage-tank B: and N, a storage-tank for the formaldehyde.

In the diagram', numerals 1 to l2 inclusive, represent lines, andthe accompanying arrows in'dicate the courses followed by the materials. The line 5 conveys' alcohol to the filter for washing purposes. It will be un- 'derstood that the filtering device E may comprise an ordinary filter or a suitable centrifuging machine. The sodium hydroxide may be introduced into thesupply tank C in solid form, in the first instance; or, it may be ldissolved in methyl alcohol, or a dilutev solution of-water, and fed into the system.

, Methylene chloride from. storage A, methyl alcohol from storage B, and sodium hydroxide from storage C are drawn into autoclave D where the alkali if used in solid form is dissolved. The mixture then is heated at 100o to 125 C., for from one to three hours in order to effect complete reaction.

The reaction product passes thence through l a filter EY where sodium chloride is removed, the filtrate going into the still Gr. Here methylal and alcohol are fractionated ofi', the former going into storage I and the latter into storage B to be used again. The st-ill residue contains the water resulting in the reaction and any excess of sodium hydroxide as well as a small amount of sodium chloride. This residual liquor goes into evaporatorl J where the water is removed, the final residue then being returned to the system through lalkali storage C as indicated by pipe K. Itis to be noted that instead of introducing solid alkali into autoclave D it may be dissolvedin the alcohol from C and introduced inJ solution. In `practice the alkali probably would,be added tothe reaction mixture in this way. l

Ie will be observed that methyl alcohol,

dnethylene chloride and sodium hydroxide the production of formaldehyde, it is passed l into the hydrolyzer L', where it is heated,

under pressure, with acidulated water to form formaldehyde and methyl alcohol. The aqueous alcoholic solution of formaldehyde goes then to still M where the alcohol is removed going backto -storage B, the formaldehyde being left behind in ythe aqueous solution. If sulphuric acid is used in the hydrolyzer all acid can be ei'ectively removed from the aqueous formaldehyde solution by treatment with barium carbonate the carbonate reacting with the acid to form barium sulphate which is insoluble andcar bonic acid which breaks down and evolves carbon dioxide. The method leads to the production of formaldehyde of high urity.

Various alkalis of the alkali meta s may be used, as, for example, sodium hydroxide, potassium hydroxide, and'lithiu'm hydroxide. It may be added, however, that lithium hydroxide is too rare and expensive, at the present time, for commercial use in the process. i

The alkali of the alkaline earth metals, for example, calcium hydroxide, Will not pass readily into solution, especially with high alcoholic concentration; hence, it is desirable to use an alkali of an alkali metal. A Any methylal can be prepared by the process, by using the appropriate alcohol, as, for example, ethyl, methyl, propyl and butyl alcohols.

Some alcohol is produced by reaction in the autoclave, and also some formate is produced. The alcohol produced is recovered; and, if desired, the formate may be recovered in any suitable manner. If desired, one may use only a slight excess of alkali, in which case the step of recovering and returning the sodium hydroxide to the source of supply may be omitted. At the evaporator J, any excess of VWater introduced into the system by reaction 'may be evaporated, or taken out of the system.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessarylimitations should be understood therefrom, but the appended claims should be construed as broadly as permissible in view of the prior art.

What I regard` as new, and desire to secure by Letters Patent, is:

1. The process ofv producing methylal which comprises causing a reaction between Y methylene chloride, alcohol and an alkali.

2. The `process of producing methylal which comprises heating methylene chloride, alcohol fand an alkali in a closed vessel, or under pressure. y

3. The process of producing'A methylal Whiclr comprises subjecting a mixture of methylene chloride, alcohol and an alkali metal compound to a temperature exceeding C. in a closed vessel or under pressure.

4. The processl of producing methylal which comprises causing a reaction between methylene chloride, alcohol and a compound of an alkali `metal, separating the salt formed in the reaction from the filtrate, and separating methylal from the filtrate by distillation.

5. The process of producing methylal which comprises subjecting a lmixture of methylene chloride, alcohol and a caustic alkali to a temperature exceeding 60 C., under pressure, separating the salt formed from the filtrate, and fractionally distilling the filtrate to separate the methylal there from. y

6. The process of producing methylal which comprises causing a chemical reaction between methylene chloride, methyl alcohol, and a caustic alkali, separating the salt formed from the filtrate, and fractionally distillin the filtrate toseparate therefrom the met ylal.

7. The process of producing methylal which comprises causing reaction between methylene chloride, v methyl alcohol and sodium hydroxide, separating the sodium chloride formed from the filtrate, and refcovering the methylal from the iltrate.

8. The process of producing methylal which comprises heating, under pressure, a mixture of methylene chloride. alcohol, and a caustic alkali, .separating the salt formed from the filtrate, and fractionally distilling the filtrate to recover the alcohol on one hand and methylal on the other.

9. The process of producing formaldehyde which comprises causing a reaction between methylene chloride, alcohol and a caustic alkali, se arating the methylal formed from the resu tant mixture, and subjectin the methylal to a hydrolyzing operation an separating the formaldehyde from the resultant products.

10. The process of producing methylal which comprises subjecting a mixture o alcohol, methylene chloride, and caustic alkali, taken, in proportions of about one hundred gallons of alcohol, ten gallons of methylene chloride and one hundred ten pounds of caustic alkali to the action of heat at a temperature exceeding 60 C., and separating the methylal formed in the reaction from the other products ofthe reaction mixture.

CARNIE B. CARTER. 

